The invention relates to a system for storing and handling pipes between a pipe rack and a derrick, and to a rig comprising such system.
Pipe stands are typically lengths of piping made up of two or more single pipes. Hereinafter, the term “pipe” refers to both single pipes as well as pipe stands.
When producing petroleum products, use is made of a drilling derrick, which forms part of a rig. The rig may be situated either onshore or offshore. Offshore, the rig may be a fixed structure standing on the seabed, or it may be a floating structure, which is either tethered to the seabed or dynamically positioned.
The main function of the drilling derrick is to provide suspension for winching equipment that is used to lower a drill string, riser, casing and other continuous pipe strings down to or into a well, as well as lifting the drill string out of the well.
A time-critical factor of drilling operations and other operations that involve lowering and retrieval of a long pipe string (also referred to as “tripping”) is the transport to and from the drilling derrick. It has therefore been desirable to store stands (consisting of 2, 3 or 4 drill pipes) as close to the derrick as possible. However, space is highly restricted in this area, as other essential equipment must also be stored here. Another argument for moving the stands away from the actual drilling deck is that placing them at a lower level would lower the centre of gravity. Thus, these storage racks near the drilling derrick can hold only a limited number of pipes.
Much effort has gone into developing equipment that will provide rapid transport of stands to the drilling derrick, in some cases directly to the drilling centre (the line followed by the pipe string through the derrick). It is equally important to be able to quickly remove pipes that have been detached from the pipe string.
Great emphasis has also been placed on the safety aspects involved in the development of this type of pipe handling equipment. Consequently more and more automated equipment has been developed, requiring a minimum number of personnel on the drilling deck (or drill floor).
One element that has been developed to make the pipe handling more efficient is the use of a so-called mousehole, which is a storage area on a drilling rig where the next joint of a (drilling) pipe is held until needed. Conventionally, the mousehole was typically located in the floor of the rig and usually lined with a metal casing known as a scabbard. Such mousehole made it possible to bring in a stand, which is then ready for subsequent transport to the drilling centre as soon as the need arises. Assembling a stand is typically done by first placing one pipe in the mousehole and then screwing another pipe down onto the top of the first pipe. This may be followed by a more pipes being screwed onto the bottom of the first two, which then have to be lifted up before this coupling operation. It is also possible to temporarily store stands that are removed from the drilling centre pending onwards transport to the pipe rack, or stands can be dismantled in the mousehole and the pipes then transported separately to the pipe rack. It is also possible to assemble/disassemble stands at the drilling centre but this will slow the tripping down considerably.
In the prior art improvements on the mousehole have also been reported. For example, U.S. Pat. No. 8,052,370B2 discloses a system for handling pipes between a pipe rack and a derrick. The derrick is located on a drilling deck, in connection with the production of petroleum products. The system comprises means of carrying pipe lengths between the rack and the derrick. It also comprises a unit at the drilling deck for temporary storage of at least two pipe lengths in respective receiving chambers. The receiving chambers can be moved to and from at least one receiving and/or hand-over position, in which position a pipe handling unit is arranged to hand over a pipe length to a receiving chamber and/or retrieve a pipe length from a receiving chamber. The up and down moving of the pipe lengths is done using one elevator for all chambers or one elevator for each chamber. The elevator is driven by a driving apparatus, which comprises a hydraulic motor and an endless chain extending between two sprocket wheels or gear wheels. The unit may be rotatable and located under an opening in the drilling deck. The problem with this pipe handling system is that it requires a lot of space, while there is not much space available on a rig, and particularly not near or in the derrick. There is thus a need for improvement of the system.